Mixtures of oil and water are usually separated by utilizing their differences in specific gravity, advantageously. Since most oils have a specific gravity substantially less than that of water, with time they separate and stratify into a surface layer of oil upon an underlying body of water. Once this occurs the oil may be skimmed off the water. By sequentially treating the residual water in this manner, the oil content of the mixture becomes less and less.
Oil-water separators are used in treating the condensate of compressed air systems. As air is compressed in oil lubricated compressors, part of the lubricating oil becomes entrained in the water condensate discharge. This type of oil is finely dispersed. The specific gravity of some of these oils is quite high, even approaching that of water. Thus, even if the condensate is allowed to settle in holding tanks for hours, such does not guarantee separation by stratification alone.
A commercially available oil-water separator used to separate the oil and water constituents of compressed air systems is the Ecosep series WT separator sold by Zander Filter Systems, Inc. of Norcross, Ga. It has a series of compartments through which oil and water is flowed in series with the liquid being drawn from a lower portion of each compartment and surface oil skimmed away. More specifically with the Zander unit the condensate from air compressors is reduced to atmospheric pressure and passed through a series of settling chambers by liquid displacement. Oil is drawn from the surface of the condensate in each chamber and residual water passed from the bottom of each chamber and then through an activated carbon filter which filters any remaining oil residue.
Though the just described type of oil and water separators have performed effectively, their activated carbon filters have had to be monitored and replaced frequently. This has been attributable to the fact that some of the oils used in air compressor systems tend to remain emulsified and do not rise to the surface of the liquid in the settling chambers. Similarly, other oils with specific gravity approaching that of water rise so slowly that they remain dispersed in the water that is displaced from chamber to chamber.
The just described problem could perhaps be solved with the use of fibrous membrane filters. However, oil and water separators that employ these are structurally complex and very expensive.
Accordingly, it is seen that a need remains for an oil and water separator and separation process that can be used and maintained in a more cost effective manner, and which is particularly well suited for use in processing the condensate from compressed air systems. It is to the provision of such therefore that the present invention is primarily directed.